In article , Brian Gaff
wrote:
Not sure, it could be climate change perhaps, but something has obviously
changed as the concrete outside my back door never had moss for over 15
years, but in the last 5 its terrible. I do not think all of a sudden
that the concrete has become more porous than it was. Maybe its sticky
water? :-)

perhaps cleaner air?

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from KT24 in Surrey, England